1. Field of the Invention
This invention relates to multilayer gaskets, and more particularly to multilayer metal gaskets including a stopper for limiting compression height of the gasket when installed between two mating surfaces.
2. Related Art
Multilayer metal gaskets, also referred to by some as multilayer steel (MLS) gaskets, are commonly used in static sealing applications that require a fluid-tight seal to be created around a passage shared by two mating members. For example, an MLS gasket, generally indicated at 20 in FIG. 1, may be clamped between a cylinder head 22 and an engine block 24 to perfect a combustion seal around multiple combustion chambers 26 as well as around oil and lubrication passages shared by the two mating members 22, 24. However, multilayer metal gaskets can also be used in other applications, such as to seal an exhaust manifold to an engine block, as well as other engine and non-engine applications. An enlarged fragmentary view of a prior art multilayer gasket 20 is shown in FIG. 2. Frequently, cylinder head gaskets 20 like that shown in FIGS. 1 and 2 include multiple bore openings to correspond with multiple combustion chambers 26 in an engine block 24. The constant transition between compression and expansion in adjacent cylinders creates substantial cyclic pressure differentials that make sealing combustion gases difficult. As a result, it is common for some combustion gases to leak through the multiple layers of the gasket 20 over time, resulting in some loss of engine efficiency.
Multilayer gaskets are particularly useful in applications that require a minimal thickness gasket capable of sealing effectively under fairly low and/or highly variable contact pressures. US Publication No. 2005/0189724, assigned to the assignee of this invention, the entire disclosure of which is hereby incorporated by reference, discloses a multilayer metal gasket including first and second functional layers formed with respective openings that coincide with a cylinder chamber. The functional layers include opposed sealing beads around the opening, together with an interposed stopper layer serving as a compression limiting feature to establish a final, i.e., fully compressed, assembled height.
One shortcoming of many prior art multilayer gasket designs may be attributed to the high cost of the stopper feature which is typically either formed of integral folds or separately formed and then attached by laser welding or some other technique. Both the fold-over stoppers and loose piece formation stoppers increase manufacturing costs, material handling complexities and increase manufacturing time. For these reasons and others, there is a need for new and improved multilayer gaskets that will meet the quality and operational characteristics demanded by modern engine technology while reducing cost and/or fabrication complexity.